A blog about Politics, Economics, and assorted random things I find interesting

12/26/2010

In the market for a digital camera? More than ever, people have turned to the convenience and low cost of digital cameras over 35mm film. Unfortunately, doing your own research often isn't very helpful-- camera manufacturers focus their marketing on gimmicks and gizmos and downplay those things that can actually distinguish one camera from another. We'll walk through all the specs that you might see in your digicam travels and explain what they mean and if they matter.

Before you dive into the rest of this article, please note that photography, like many other things is subjective. There is no "best" camera. Photography is visual, and each individual person perceives that sensory input differently. Every camera has a slightly different "look" to the images that will never show up on the spec sheet. Trust your eyes and go with what you like. Specs are nice and can point you one direction or another, but follow your instinct when you a certain camera's images So, here we go!What Matters What matters most in a camera depends on what you are photographing. Since most people take most of the pictures of people, I will target my comments accordingly. The most important feature for a camera to have is quick response. This means that when you push that button down, the camera is focused and accurately metered. If it has to stop and think for even an instant, then the moment will be gone. Photo editing after the fact can change color balance, sharpen an image, and work near miracles to your photos. But NOTHING can change an expression or switch the captured moment to the one you *really* wanted to capture. Because response matters so much, then those camera factors that determine response will be at the top of the list:

Autofocus Speed & Accuracy

High ISO Capability/Range

Shutter Lag

Autofocus speed matters because most cameras won't intentionally take an out-of-focus picture. Unless it's in focus, it won't take the picture until the moment is gone. Accuracy of autofocus matters similarly- if the focus is easily confused, it takes more time. You *need* focusing that's instant and dead-on, every time. ISO capability is just a measure of light sensitivity. There are two components to this aspect: how high the values go, and how good the images look as the numbers go up. Higher ISO capability allows faster shutter speeds, and this makes your images sharper and less prone to blur from people movement. Be advised that just because the ISO is listed as going all the way to 1600, it doesn't mean that this high setting is useful. Many cameras have too much "noise" at elevated settings to be useful. You want the maximum ISO with acceptable noise. This "noise" is equivalent to the hissing sound you hear between songs when the stereo is cranked up-- it's an artifact of having to crank up the "volume" on the sensor so much. Almost always, a larger size sensor is better. Why is a larger sensor size better? A larger sensor catches more light in a given amount of time. Both a spoon and a shovel can be used to move a dirtpile, but which will do it faster? A larger sensor size captures "enough" light in far less time, making image capture in low light or fast action situations far better. Sensor size is typically quoted as a fraction of a square inch, like 1/1.7 sq inch. The smaller the second number (denominator), the larger the sensor and the faster it will be. Finally, shutter lag is just the time between when you press the button and when the image is captured. Pro cameras have nearly instantaneous response, but you'll pay for that. Go with the fastest you can afford.

After response, the remaining performance aspects of a digital camera are far less important. Least important of all is resolution (the megapixels). This is probably the opposite of what you've been led to believe. Indeed, the marketing departments of every maker of digicams have pushed this ridiculous myth year after year as resolutions get higher. But how much do you really need? That's actually rather easy to figure out, as the math is straightforward. If you have a computer screen with 1280x800 resolution (a common laptop resolution), then you'd need 1280x800= 1,024,000 pixels-- or an underwhelming ONE MEGAPIXEL! Yes, a single measly megapixel will completely fill a laptop screen, and a very large 24" display running 1920x1200 only needs 2.3Mp. If you decide you want to make prints of your photos, you'll need more resolution. But you'll only need enough to make the ensure the printer's capability is the limiting factor. So if your printer can print 300dpi (dots per inch) and you want to print an 8x10, you'll need 8(x300) x 10(x300) or 2400x3000 resolution. This is 7.2Mp. Generally speaking, you will never need more than 8Mp resolution. This is because as you print larger and larger, you will view if from farther and farther away, reducing the needed resolution accordingly. Sure, 100dpi doesn't look sharp at point blank range, but you won't be viewing a 22x30 print at arm's length anyway-- it won't matter. So all the manufacturers stick you with more resolution than you need. Now, this would normally be OK, but like many things in life, this is one area where getting something for free really isn't free. That extra resolution ends up reducing the ISO sensitivity of the sensor. How so? Cramming extra sensing elements on the same size sensor reduces the amount of light that falls on each one-- just like trees in a crowded forest get less light because the neighboring trees steal some of it. This means it takes more total exposure to the light to "charge" the sensor sufficiently. This would be like the trees growing more slowly in a crowded forest. The price of "free" extra resolution is noise and reduced ISO capability, all else being equal. This is why pro cameras with "full frame" sensors are so stunningly responsive and capable of superb high ISO performance.

Finally, we lump together all the intangibles, gadgets, gizmos, and gimmicks to weigh our decision on a camera. Lighter is better. Faster is better. Longer battery life is better. Good feel in the hand is important. Shake reduction/image stabilization is important. Buttons for key functions instead of 20 levels of sub-menu saves a lot of time. Face detection can help your people pictures turn out right the first time.